1. Field of the Invention
The present invention relates to a vibration type driving apparatus and a driving circuit of the vibration type driving apparatus, and particularly, relates to a so-called ultrasonic motor in which an elliptic motion is formed on the surface of a vibrating body by an electrical-mechanical energy converting element to perform a relative movement between the vibrating body and a moving body, which is used for lenses for cameras, office automation (OA) equipment, or the like, and a driving circuit of the ultrasonic motor.
2. Description of the Related Art
Nowadays, vibration type actuators (vibration type driving apparatuses) that vibrate a vibrating body using a distortion generating element that generates mechanical distortion as an electric field or a magnetic field is exerted, and convert the vibration of the vibrating body into a continuous or intermittent mechanical motion and output the motion are used in various fields.
An actuator referred to as an ultrasonic motor among piezoelectric actuators utilizing a piezoelectric element is able to constitute a rotary drive source of continuous rotation type.
Because of this, this rotation drive source has already been mounted on optical instruments, such as a camera, as a drive source that replaces a rotary electromagnetic drive motor of the related art, and the driving control technique of such an ultrasonic motor has also been substantially established.
Although the technique regarding the ultrasonic motor has been substantially established, the technique of stabilizing efficiency requires further improvements.
Vibration type driving apparatuses (ultrasonic motors) that excite the vibration of equiform bending modes within a plurality of different planes are disclosed in, for example, Japanese Patent Application Laid-Open No. H04-091671 and the like, and the driving principle or the like thereof is described in detail in these publications.
Vibrating bodies disclosed in these publications include an electrical-mechanical energy converting element and an elastic member.
The vibrating body sandwiches and fixes the electrical-mechanical energy converting element with the elastic member from both sides.
Driving of the vibration type driving apparatuses that excites the vibration of such equiform bending modes within the plurality of different planes is allowed by generating an elliptic motion on surface particles of the vibrating body and continuously driving a moving body that is brought into pressurized contact with this vibrating body.
Pattern electrodes are formed on the piezoelectric element, and substantially sinusoidal alternating voltages that are sequentially different in time phases by 90° are applied to the respective electrodes.
If alternating voltages are applied in a frequency near the natural vibration of a vibration mode to be excited, the vibrating body resonates due to a bending moment applied to the vibrating body by the expansion and contraction of the piezoelectric element.
The vibration modes that are respectively excited with respect to the alternating voltages that are different by 90° are equiform and are different in phase, and an elliptic motion is formed on the surface particles of the vibrating body by the synthesis of the modes.